Systems and methods are provided that employ two or more cryptographically linked codes. The codes, when encrypted, become cipher texts that appear unrelated. The codes described herein are characterized by a series of bits including one or more switch bits. The cipher text of a code having a switch bit in one state will appear to be unrelated to the cipher text of another code differing only in that the switch bit is in the opposite state. The cryptographically linked codes can be used in various combinations, such as on a product and its packaging, on a product and a component of the product, on a certificate packaged with the product and on the packaging, or on outer and inner packagings of the product.